In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.
-Give genotypes for comb shape of the parents in the following cross: Pea crossed with single produces 1 single offspring.
A) rr PP × rr pp
B) RR Pp × rr pp
C) Rr PP × rr pp
D) Rr Pp × rr pp
E) rr Pp × rr pp

Question

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced. 
-Give genotypes for comb shape of the parents in the following cross: Pea crossed with single produces 1 single offspring.
A) rr PP × rr pp
B) RR Pp × rr pp
C) Rr PP × rr pp
D) Rr Pp × rr pp
E) rr Pp × rr pp

Quizplus · Accepted Answer

The pea comb parent must have the genotype rr Pp to produce a single comb offspring (rr pp) when crossed with a single comb parent (rr pp).

In Chickens, Comb Shape Is Determined by Genes at Two